It is old in the art to provide a low speed continuous run feature for a double facer machine. A double facer machine is preferably continuously operated at low speeds during adjustments of the slitter-scorer and cut-off as may be required for change over from one form or size of box blank to another at the end of a production run. In accomplishing this result, the double faced web is severed as its leaves the double facer machine and the speed of the double facer machine is then immediately reduced relative to the speed of the previously formed web so as to afford an increasing gap between the severed ends of the web. After the desired adjustments have been made to the slitter-scorer and cut-off, the speed of the double facer machine and the speed of the entire corrugator may be adjusted or increased as required. For relevant prior art, see U.S. Pat. Nos. 2,764,217 and 2,950,658.
While the prior art devices have performed satisfactorily, they have certain limitations which are overcome by the present invention. In U.S. Pat. No. 2,950,658, speed control is attained by way of the differential shown in FIG. 3 and which is expensive as well as being comprised of many components. This invention involves fewer components and attains the desired result at a substantially lesser cost. Further, the prior art lacked safety features which are provided by the present invention.
The prior art sought to use a single drive motor for driving the double facer machine in the high speed run mode and in the low speed mode. It is more efficient and less expensive to use two discrete motors, each designed to drive the double facer machine at one of the different speed modes.